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PIWebAPI performance issues.

Question asked by CarlB on May 29, 2020

Hello everyone!

We're running into a periodic or sporadic issue with our PI Web API servers. There are two PI Web API 2019 servers (v. 1.12.0.6145) servers sitting behind a BigIP LTM for load balancing. Both are running on Windows Server 2016 standard with 8gigs of memory. Nothing else is running on these servers. I think I've ruled out the load balancer as we experience the issue whether we are making calls directly to an individual server or via the load balancer.

 

The calls were are making are pretty simple, just a call to the streams controller and getend action. Each call returns about 600 bytes. We're looping through an array of about 15 web ids and making the call using jquery's $.ajax method.

 

Here is a sample call:

https://<servername>/piwebapi/streams/<webid>/end?selectedFields=Value;UnitsAbbreviation;Good;

 

It seems to be that if the PIWebAPI is idle for long enough, the first call will take between 15 and 40 seconds. Subsiquent calls have sub-second response times. I'm guessing the subsiquent calls are faster due to caching, but why is that initial set of calls taking so long? And is there any way to speed it up?

 

Thanks!
Carl

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